Amino derivatives of pyrazolopyridine carboxylic acids and esters

ABSTRACT

New amino derivatives of pyrazolo(3,4-b)pyridine-5-carboxylic acids and esters have the general formula   THEY ARE USEFUL AS ATARACTIC, ANALGESIC AND ANTIINFLAMMATORY AGENTS. In addition, the new compounds increase the intracellular concentration of adenosine-3&#39;&#39;,5&#39;&#39;-cyclic monophosphate.

Ilnite States Patent [191 Hoehn at al.

[ Aug. 28, 1973 Bayreutherstrasse l3, Nurnberg, both of Germany 22Filed: Aug. 5, 1971 211 App]. No.: 169,536

Related US. Application Data [63] Continuation-impart of Ser. No.41,568, May 28,

1970, abandoned.

[52] US. Cl. 260/295.5 B, 260/250 A, 260/268 BC, 260/256.4 R, 260/294.8C, 260/293.6, 424/250, 424/25 1 424/266, 424/267 [51] Int. Cl C07d 31/36[58] Field of Search 260/295.5 B, 294.8 B

[56] References Cited OTHER PUBLICATIONS Chem. Abstracts, Vol. 69, No.17, 67, 376-v, Oct. 21, 1968 Primary Examiner-Alan L. RotmanAttorney-Lawrence S. Levinson, Maria Smith et al.

[57] ABSTRACT New amino derivatives of pyraz0l0[3,4-b]pyridine-S-carboxylic acids and esters have the general formula they are useful asataractic, analgesic and antiinflammatory agents. In addition, the newcompounds increase the intracellular concentration of adenosine- 3 ',5-cyclic monophosphate.

22 Claims, No Drawings AMINO DERIVATIVES F PYRAZOLOPYRIDINE CARBOXYLICACIDS AND ESTERS This application is a continuation-in-part ofapplication Ser. No. 41,568 filed May 28, 1970 now abandoned.

SUMMARY OF THE INVENTION This invention relates to new amino derivativesof pyrazolol3,4-blpyridine-S-carboxylic acids, their esters and salts ofthese compounds as well as processes for producing them. These newcompounds have the formula The symbols have the following meanings informula I and throughout this specification. R is hydrogen or alkyl upto 12 carbon atoms, R, is hydrogen, lower alkyl, phenyl, phenyl-loweralkyl,benzoyl or substituted benzoyl, R is hydrogen, phenyl or lowralkyl. The basic nitrogen group is an acyclic amino group wherein R andR each is hydrogen, lower alkyl, lower alkenyl, lower alkanoyl, phenyl,substituted phenyl (i.e., the phenyl ring contains one or two simplesubstituents including lower alkyl, halogen, trifluoromethyl, amino orcarboxy, preferably onely one of the latter three substituents),phenyl-lower alkyl, di-lower alkylamino-lower alkyl, benzoyl,substituted benzoly, phenyl-lower alkanoyl, substiuted phenyl-loweralkanoyl, alkanesulfonyl, benzenesulfonyl or substitutedbenzenesulfonyl. The substitutents on the phenyl groups being the sameas above (preferably only one of the last groups). This basic group mayalso form a heterocyclic of 5- or 6 -members in which an additionalnitrogen is present, i.e., the pyrrolidino, piperidino, pyrazolyl,pyrimidinyl, pyridazinyl, dihydropyridazinyl or piperazinyl radicals,each of which may also hear as a substituent a hydroxy-lower alkyl groupor one or two lower alkyl groups. That is to say, R, and R each ishydrogen, lower alkyl, R,, R,- phenyl (wherein R, and R, each ishydrogen, halogen, lower alkyl, amino, trifluoromethyl or carboxy),phenyl-lower alkyl, R k phenyl-lower alkyl, di-lower alkylamino-loweralkyl, benzoyl, R R,-benzoyl, phenyl- .lower alkanoyl, RR-,-phenyl-lower alkanoyl, lower alkylsulfonyl, benzenesulfonyl, R R-benzenesulfonyl or R, and R together with the nitrogen to which theyare attached form one of the heterocyclics mentioned above or the R-monosubsituted or R,,, R disubstituted derivative (wherein R and R, arelower alkyl or hydroxy-lower alkyl). R, is hydrogen, lower alkyl,phenyl, substituted phenyl, phenyl-lower alkyl and substitutedphenyl-lower alkyl.

The lower alkyl groups in any of the foregoing radicals are straight orbranched chain hydrocarbon groups of up to seven carbon atoms likemethyl, ethyl, propyl, isopropyl, butyl, t-butyl and the like. The loweralkenyl are similar groups with one double bond. in the case of R, thealkyl group is of the same type having up to 12 carbon atoms.

All four halogens are contemplated but chlorine and bromine arepreferred.

The lower alkanoyl groups are the acyl groups of the lower fatty acids.

The products of the examples, which are representative of the variouscompounds of this invention, consti tute preferred embodiments.Preferably R is hydrogen, particularly when R; includes a cyclicsubstituent. Especially preferred compounds of formula I are thosewherein R is hydrogen or lower alkyl, especially ethyl, R is hydrogen,methyl, ethyl or butyl, R is hydrogen or methyl, R is ethyl, propyl orbutyl, R is hydrogen or ethyl and R is hydrogen or lower alkyl,especially methyl.

DETAILED DESCRIPTION The new compounds of formula I may be produced byseveral methods.

A. According to one procedure, when R is other than hydrogen, a productof formula I may be produced from compounds of the formula (|)10weralkyl R COOR N i Rs 40 R1 II or from compounds of the formula R;H" C 001 N -n- /y a 1& m

where X is chlorine or bromine.

The compounds of formula II are produced by the method described incopending application, Ser. Nov 833,672, filed June 16, 1969, i.e.,producing a 5- aminopyrazole of the formula (IV) by ring closure of analdehyde or ketone hydrazone of the formula wherein R and R each ishydrogen, lower alkyl, phenyl or phenyl-lower alkyl. This is effected byheating at a temperature of about 90 to 130C. in an inert liquid solventlike butanol or ethanol preferably in the presence of an alkali metalalcoholate catalyst.

The S-aminopyrazole of formula IV is made to react with analkoxymethylene malonic acid ester of the formula C Oalkyl CO Oalkyl byheating at a temperature of about 120C. The resulting compound of theformula is cyclized in an inert organic solvent such as diphenyl etherat about 230 to 260C. while distilling off the alcohol formed, producinga compond of formula II with a hydroxy group in the 4-position insteadof the 0- lower alkyl group. This is then alkylated by treatment with analkyl halide in an inert organic solvent like dimethylformamide in thepresence of an alkali metal carbonate to obtain a compound of formulaII.

Instead of alkylating the 4-hydroxy compound referred to above, this4-hydroxy compound may be refluxed for several hours with a phosphoroushalide like phosphorus oxylchloride to obtain the intermediate offormula I".

Alternatively, instead of cyclizing the malonic acid ethyl estercompound of formula VII in an inert organic solvent at about 230 to 260as described above, this product also undergoes cyclization by treatmentwith phosphorous oxychloride producing directly the intermediate offormula III.

Derivatives of formula I in which R is other than hydrogen may also beprepared by reacting a 5- aminopyrazole of formula IV with an acylmalonic acid ethyl ester of the formula C O Oalkyl Win) at a temperatureof about 1 10l 30 in the presence of poly-phosphorous acid.

The products of formula I are then produced from eitherof the compoundsof formula II or formula III by reaction with the appropriate primary orsecondary amine of the formula IIN R; VIII) This reaction is effected bytreating the reactants either at room or elevated temperatures. For somecases it may be advantageous to make use of an autoclave.

B. According to a modification of the foregoing procedure, a product offormula I wherein R is hydrogen may be produced. By this modification, a5- aminopyrazole of formula IV wherein R is an arylmethyl group or aheteromethy] group is used. This starting material has the formula.

At this point, the compound of formula II having in the lposition the-CI-I,R, substituent of formula lVa is oxidized with an oxidizing agentlike selenium dioxide in a high boiling solvent like diethyleneglycoldimethylether at about 160C. This yields a compound of formula IIwherein R is hydrogen and this product may be treated with the primaryor secondary amine as described above.

Instead of alkylating the compound of formula II with the 4-hydroxygroup, this may first be oxidized to remove the l-substituent and thenalkylated in the 4- position.

C. According to another method, a product of formula I wherein R ishydrogen or other than hydrogen may be produced by cyclizing with anunsubstituted or substituted hydrazine of the formula a4-amino-2-halo-5-alkoxycarbonylpyridine of formula X or formula XI asfollows:

[produced by reacting 3-iminobutyronitrile with hydroxylamine by theprocedure described in Ann.

Chem. 624, 22 (1959)] is made to react with an alkoxymethylene malonicacid ester of the same formula as Vl above by heating at a temperatureof about 120C.

The resulting compound of the formula (XII) C O O-allryl (XIII) iscyclized in an inert organic solvent, under the same conditions as thecompound of formula VII above is treated, similarly producing a compoundof formula RT COOR with a hydroxy group in the 4-position. This is thensimilarly alkylated by treatment with an alkyl halide in an inertorganic solvent like dimethylformamide in the presence of an alkalimetal carbonate to obtain a compound of formula The 4-hydroxy compoundin this series too, instead of being alkylated may be refluxed forseveral hours with a phosphorous halide like phosphorous oxychloride toobtain the intermediate of formula (XVI) The compound of formula XVII isthen hydrogenated with a catalyst like Pd on charcoal in an organicsolvent like acetic acid to form a compound of the formula Treatment ofthe compound of formula XVIII with a phosphorous oxyhalide likephosphorous oxychloride or oxybromide in an organic solvent like benzeneyields a compound of formula X or more vigorous treatment of thecompound of formula XVIII in a base like pyridine yields a compound offormula XI. Treatment of either of these intermediates with a hydrazine,as described above, yields the new products of formula I.

The compounds of formula I form salts which are also part of thisinvention. The salts include acidaddition salts, particularly thenon-toxic, physiologically acceptable members. The bases of formula Iform salts by reaction with a variety of inorganic acid organic acidsproviding acid addition salts including, for example, hydrohalides(especially hydrochloride and hydrobromide), sulfate, nitrate, borate,phosphate, oxalate, tartrate, malate, citrate, acetate, ascorbate,succinate, benzenesulfonate, methanesulfonate,cyclohexanesulfamate andtoluenesulfonate. The acid addition salts frequently provide aconvenient means for isolating the product, e.g., by forming andprecipitating the salt in an appropriate menstrumm in which the salt isinsoluble, then after separation of the salt, neutralizing with a basesuch as barium hydroxide or sodium hydroxide, to obtain the free base offormula I. Other salts may then be formed from the free base by reactionwith an equivalent of acid.

The new compounds of this invention are central nervous systemdepressants and may be used as tranquilizers or ataractic agents for therelief of anxiety and tension states, for example, in mice, cats, rats,dogs and other mammalian species, in the same manner as chlordizepoxide.For this purpose a compound or mixture of compounds of formula 1, ornon-toxic, physiologically acceptable acid addition salt thereof, may beadministered orally or parenterally in a conventional dosage form suchas tablet, capsule, injectable or the like. A single dose, or preferably2 to 4 divided daily doses, provided on a basis of about 1 to 50 mg. perkilogram per day, preferably about 2 to 15 mg. per kilogram per day, isappropriate. These may be conventionally formulated in an oral orparenteral dosage form by compounding about to 250 mg. per unit ofdosage with conventional vehicle, excipient, binder, preservative,stabilizer, flavor or the like as called for by accepted pharmaceuticalpractice.

The new compounds also increase the intracellular concentration ofadenosine-3',5'-cyclic monophosphate, and thus by the administration ofabout 1 to 100 mg/kg/day, preferably about 10 to 50 mg/kg., in single ortwo to four divided doses in conventional oral or parenteral dosageforms such as those described above may be used to alleviate thesymptoms of asthma.

The new compounds of this invention, in addition, have antiinflammatoryand analgesic properies and are useful as antiiflammatory agents, forexample, to reduce local inflammatory conditions such as those of anedematous nature or resulting from proliferation of connective tissue invarious mammalian species such as rats, dogs and the like when givenorally in dosages of about 5 to 50 mg/kg/day, preferably 5 to 25mglkg/day, in single or 2 to 4 divided doses, as indicated by thecarageenan edema assay in rats. The active substance may be utilized incompositions such as tablets, capsules, solutions or suspensionscontaining up to about 300 mg. per unit of dosage of a compound ormixture of compounds of formula I or physiologically acceptable acidaddition salt thereof. They may be compounded in conventional mannerwith a physiologically acceptable vehicle or carrier, excipient, binder,preservative, stabilizer, flavor, etc. as called for by acceptedphannaceutical practice. Topical preparations containing about 0.01 to 3percent by weight of active substance in a lotion, salve or cream mayalso be used.

The following examples are illustrative of the invention. Alltemperatures are on the centrigrade scale.

EXAMPLE 1 4-amino-1-ethyl-1H-pyrazolo[3 ,4b]pyridine-5- carboxylic acidethyl ester a. [[(1-ethyl-5-pyrazoly1)amino]methylene]malonic aciddiethyl ester Two hundred and forty-five g. 1-ethyl-5- aminopyrazole(2.2 mole) and 476 g. ethoxymethylene malonic acid diethyl ester (2.2mol.) are heated to 120 (bath temperature) for 2 hours with stirring.The ethanol formed by this reaction is removed by means of a wateraspirator. Then vacuum distillation (b.p. 0.1 154- -160) yields 520 g.(84 percent of theory) of a quick crystallizing oil of 1-ethy1-5-pyrazolyl)amino]methylene] malonic acid diethyl ester, m.p. 50-53.

The compound is recrystallized from N-hexane, m.p. 5557.

The hydrochloride salt is formed by treating the above product withdilute ethanolic hydrogen chloride solution.

b. l-Ethyl-4-hydroxy-1H-pyrazolo[3,4-b]pyridine-5- carboxylic acid andethyl ester I Two hundred and fifty-three g. [[(1-ethyl-5-pyrazolyl)amino]methylene] malonic acid diethyl ester (0.09 mol.) aredissolved in 770 g. of diphenyl ether. The reaction mixture is heated to235250 (bath temperature) and allowed to react at this temperature of1-2 hours while the resulting ethanol is continuously distilled off. Thelast amount of alcohol is removed by means of a water aspirator. Thediphenyl ether is separated by distillation with a fractionating columnin vacuo. The 1-ethyl-4-hydroxy-1H-pyrazolo[3,4-b]-pyridine-S-carboxylic acid ethyl ester is obtained at b.p. 0.05 l15-l20,yield 195 g. 92 percent of theory, m.p. 85-87. The compound isrecrystallized from benzene to m.p. 8789. Hydrolysis of this productwith aqueous sodium hydroxide yields l-ethyl- 4-hydroxy-1H-pyrazolo[3,4-b]pyridine-5 -carboxylic acid, m.p. 20l202.

c. 4-Ethoxy-1-ethyl-1H-pyrozolo[3,4-b1pyridine-5- carboxylic acid andethyl ester.

In a solution of 259 g. (1.1 mol.) 1-ethyl-4-hydroxy-1I-I-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester in 1,700 ml.dimethylformamide, 400 g. of well pulverized potassium carbonate and 300g. of ethyl iodide are introduced. The reaction mixture is stirred for 7hours at 65 and filtered under suction, while hot, from excess potassiumcarbonate. Upon standing overnight, g. of4-ethoxy-1-ethyl-1I-I-pyrazolo[3,4- blpyridine-S-carboxylic acid ethylester crystallize out of the solution, m.p. 1l21l5. After evaporation ofthe mother liquor, an additional 80 g. are obtained. The total yieldamounts to 85 percent of theory. The compound is recrystallized frombenzene (90-100), m.p. 1 131 15.

By hydrolyzing this product as in part (b) 4-ethoxy-1-ethyl-1I-I-pyrazolo[3,4-b]pyridine-5-carboxylic acid is obtained, m.p.l98l99. d. 4-amino-l-ethyl-lH-pyrazolo[3,4-b]pyridine-5- carboxylic acidethyl ester 10.4 g. of 4-ethoxy-l-ethyl-lH-pyrazolo[3,4-b]pyridine--carboxylic acid ethyl ester (0.04 mol.) and 50 ml. of analcoholic solution of ammonia (56.5 g. of ammonia in 1,000 ml. ofethanol) are heated in an autoclave at 65 for hours. After cooling thereaction mixture to room temperature, the solid product is filteredunder suction, washed with a small amount of ethanol and dried at 80.The 4-amino-l-ethyl-lH- pyrazolo[3,4-b]pyridine-5-carboxylic acid ethylester, m.p. 180 weighs 7.4 g. (90 percent), and is recrystallized fromabsolute ethanol, m.p. l8ll 82. By evaporation of the mother liquor anadditional 0.8 g. of crude product is isolated. Total yield 96 percent.

EXAMPLE 2 4-Butylaminol -ethyll H-pyrazolo 3 ,4-b pyridineS carboxylicacid ethyl ester a. 4-Chlorol -ethyll H-pyrazolo[ 3 ,4-b]pyridine-5-carboxylic acid, ethyl ester.

A mixture of 23.5 g. of l-ethyl-4-hydroxy-lH-pyrazolo-[3,4-b1pyridine-5-carboxylic acid ethyl ester (0.1 mol.) and150 ml. of phosphorous oxychloride is refluxed for 4 hours. Subsequentlythe excess phosphorus oxychloride is removed by means of vacuumdistillation. As soon as the phosphorous oxychloride has been removed,the oily residue solidifies on cooling. It is treated with water andfiltered under suction (24.5 g.), m.p. 55-60. The 4-chloro compound isrecrystallized from N-hexane (22.5 g. 87 percent), m.p. 62. b.4-Butylaminol -ethyl-l H-pyrazolo[ 3 ,4-b lpyridine- S-carboxylic acidethyl ester To a solution of 5.08 g. of 4 -chloro-l-et'hyl-1H-pyrazolo-[3,4-b]pyridine-5-carboxylic acid ethyl ester (0.02 mol.) inml. of benzene are added 2.92 g. of n-butylamine(0.04 mol.). Thismixture is kept at room temperature for 3 days. After this time, theseparated butylamine hydrochloride is filtered under suction and thefiltrate is evaported in vacuo to dryness. The residue, 4-butylaminol-ethyll H-pyrazolo[ 3 ,4- blpyridine-S-carboxylic acid ethyl ester, isrecrystallized from hexane, m.p. 8283. The total yield amounts to 5.3 g.9 l.5 percent of theory.

EXAMPLE 3 lEthyl-4-phenylaminol H-pyrazolo[ 3,4-blpyridine-5- carboxylicacid and ethyl ester.

l0.l g. of 4-chloro-l ethyl-lH-pyrazolo[3 4- blpyridine-S-carboxylicacid ethyl ester [prepared as in Example 2a (0.04 mol.)] and 20 ml. ofaniline are stirred for 2 hours at 1 l0. The excess aniline is distilledoff in vacuo and the residue is treated with sodium bicarbonatesolution. The mixture is then extracted three times with 100 ml. ofchloroform, the chloroform layer is separated, dried over sodium sulfateand concentrated in vacuo. The residue solidifes on cooling and isrecrystallized from ethanol-water. The yield of l-ethyl- 4-phenylaminolH-pyrazolo-[ 3 ,4-b lpyridine-S carboxylic acid ethyl ester is 9.2 g.percent, m.p. 96-97. Hydrolysis of this product with aqueous sodiumhydroxide yieldsl-ethyl-4-phenylamino1l-lpyrazolo[3,4-bI-pyridine-5-carboxylic acid,m.p. 237-38.

EXAMPLE 4 l-Ethyl-4-pyrrolidinol H-pyrazolo 3 ,4-b pyridine-5-carboxylic acid, ethyl ester hydrochloride By treating thel-ethyl-4-chloro-lH-pyrazolo[3,4- blpyridine-S-carboxylic acid ethylester of Example 20 with pyrrolidine and benzene as in Example 212,l-ethyll H-4-pyrrolidinol H-pyrazolo- [3,4-b]pyridine-S-carboxylic acidethyl ester is obtained. Yield 92 percent, m.p. l05l06 (cyclohexane).

The hydrochloride is formed by adding to a solution containing 5 g. ofthe above obtained 4-pyrrolidinocompound in 50 ml. of anhydrous ether,with cooling, 3.5 ml. of an alcoholic solution of hydrogen chloride (6.3N). A white crystalline precipitate forms immediately. The mixture isfiltered and washed with anhydrous ether. The product is allowed to dryat Yield =5.3 g. (93.5 percent), m.p. l90l9l.

The following compounds are prepared by the procedure of Example 1, 2 or3:

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EXAMPLE 56 4-Butylamino-11-l-pyraz01o[3 ,4-b] pyridinecarboxylic acidethyl ester a) 1-(2-fury1)methyl-S-pyrazolyl]amino]methylene]- malonicacid diethyl ester One hundred and sixty-three g. of l-(2-furyl)methyl-S-aminopyrazole (1 mol.) and 216 g. of ethoxymethylene malonic aciddiethyl ester (1 mol.) are heated to 130 (bath temperaure) until thetheoretical amount of alcohol is distilled off. The remaining oil,[[[1-(2- furyl)methy1-5-pyrazo1y]amin0]methylene]malonic acid diethyester, is recrystallized from methanol, yield 280 g. (84 percent) m.p.8486.

b. 4-hydroxy-1-(2-furyl)methyl-1H-pyrazolo[3 ,4- b]pyridine-5-carboxylicacid ethyl ester Two hundred and fifty g. of [[[1-(2-furyl)methyl-5-pyrazolyl]amino]methylene]-malonic acid diethyl ester (0.75 mol.) aredissolved in 1 liter of diphenyl ether and heated to 240 for 2 hours.The ethanol formed is continuously distilled off. The solvent is removedin vacuo. The4-hydroxy-l-(2-furyl)methyl-1l-lpyrazolo[3,4-b]-pyridine-5-carboxylicacid ethyl ester remains and is recrystallized from methanol, yield 248g. (86 percent), m.p. 103-106.

c. 4Ethoxy-1-(2-furyl)methyl-lH-pyrazolo[3 ,4- b]pyridine-5-carboxylicacid ester Three hundred g. of 4-hydroxy-1-(2-furyl)methyl-1H-pyrazo1o[3,4-bl-pyridine-S-carboxylic acid ethyl ester 1.05 mol.) aredissolved in 1 liter of dimethylfonnamide. 210 g. of potassiumcarbonate(l.5 mol.) and 233 g. of ethyl iodide are added. The mixture isheated at 60 with continuous stirring for hours. The excess potassiumcarbonate is filtered off. On addition of 500 ml. of water,4-ethoxy-l-(2-furyl)methyl-1H- pyrazolo[3,4-b]pyridine-5-carboxylic acidethyl ester precipitates and is recrystallized from methanol, yield 280g. (85 percent), m.p. 93-96.

d. 4-Ethoxy-1H-pyrazolo[3,4-b]pyridine carboxylic acid ethyl ester 3 1.5of 4-ethoxy-1-(2-furyl)methyl-11-1-pyrazolo[3,4-b]-pyridine-5-carboxylic acid ethyl ester (0.1 mol.) and 20g. of selenium dioxide (0.18 mol.) are suspended in 100 ml.diethylene-glycol dimethylether. Themixture is heated with stirring at160 and a few drops of water are .added. The temperature is kept for 1.5hours. After cooling, 100 ml. of water are added and the mixture isneutralized with a dilute solution of aqueous ammonia. Yellow crystalsare formed, which yield on recrystallization from methanol 15.8 g. of4-ethoxy-11-1-pyrazo1o[3,4-b1pyridine-5- carboxylic acid ethyl ester (67percent), m.p. 180.

e. 4-Butylamino-1H-pyrazolo[3,4-b]pyridine-5- carboxylic acid ethylester 2.35 g. of 4-ethoxy-lH-pyrazolo[3,4-bJpyridine-5- carboxylic acidethyl ester (0.01 mol.) are treated with 2.2 g. of butyl-amine (0.03mol.) at 90 for 1 hour. After this period the mixture is cooled, dilutedwith 20 ml. of water and the white crystalline precipitate is filteredoff. Recrystallization from diethyl ether yields 1.7 g. of4-butylamino-1H-pyrazolo[3,4-b1pyridine-5- carboxylic acid ethyl ester(72 percent), m.p. 181.

EXAMPLE 57 one hundred and seventy-four g. of 1-(4-pic01y1)-5-aminopyrazole and 216 g. of ethoxymethylene malonic acid diethyl esterare heated with stirring at 140, until the theoretical amount of alcoholhas distilled off. The reaction mixture crystallizes on cooling.Recrystallization from ethyl acetate yields 220 g. of [[[1-(4-picolyl)-5-pyrazolyl]amino]methylcne]malonic acid diethyl esterpercent), m.p. 97. b. 4-hydroxy-1-(4--picolyl)-1l-l-pyrazo1o[3,4-b]pyrldine-S-carboxylic acid ethyl ester Eighty-six g. of1-(4-pic0ly1)-5- pyrazolyl]amino]mcthylene]malonic acid diethyl ester(0.25 mol.) are heated at 240 for 15 minutes. The dark oil is cooled and200 ml. of methanol are added. 4- hydroxy-l-(4-picolyl)-1H-pyrazolo[3,4-b]pyridine-5- carboxylic acid ethyl ester crystallizes on standing,yield 33 g. (44 percent), m.p. c. 4-hydroxy- 1 H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester Three g. of4hydroxy-l-(4-pic01yl)-1H- pyrazolo[3,4-bJ-pyridine-S-carboxylic acidethyl ester (0.01 mol.) are dissolved in 20 ml. of acetic acid. 2.2 g.of selenium dioxide (0.02 mol.) and 23 drops of water are added. Themixture is refluxed for 30 minutes and then filtered off.4-hydroxy-lH-pyrazo1o[3,4- b]pyridine-S-carboxylic acid ethyl esterprecipitates on cooling. Recrystallization from acetic acid yields 1,8g. (87 percent), m.p. 275. d.4-ethoxy-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester I 4.1g. of 4-hydroxy-lH-pyrazolo[3,4-b]pyridine-5- carboxylic acid ethylester (0.02 mol.), 5.6 g. of potassium carbonate (0.04 mol.) and 3.5 g.of ethyl iodide (0.022 mol.) are heated in 30 ml. of dimethylformamidewith stirring for 10 hours at 60. After this time, the excess potassiumcarbonate is filtered off and 30 m1. of water areadded.'4-Ethoxy-1H-pyrazolo]3,4- b]pyridine-S-carboxylic acid ethyl esterprecipitates and is recrystallized from methanol, yield 2 g. (42.5percent), m.p. 180. e. 4-Diethylamino-1H-pyrazolo[pyrazolo[3 ,4-b]pyridine-S-carboxylic acid ethyl ester 1.2 g. of4-e'thoxy-1H-pyrazolo[3,4-blpyridine-5- carboxylic acid ethyl ester(0.05 mol.) and 1.4 g. of diethylamine (0.02 mol.) are heated at 70 for30 min utes. The addition of 5 ml. of water precipitates 4-diethylamino-ll-l-pyrazolo[3,4-b]pyridine 5- carboxylic acid ethyl esterwhich is filtered off and washed with water, yield 0.8 (61 percent),m.p. 186.

EXAMPLE 58 4-Butylamino-1 l-l-pyrazo1o[3,4-b]pyridine-5- carboxylic acid2.6 g. of 4-butylamino-1H-pyrazolo[3,4-b]pyridine- S-carboxylic acidethyl ester (0.01 mol.) are treated with 1.1 g. of sodium hydroxide in30 ml. of ethanol for 20 hours at room temperature. The solvent isremoved in vacuo and the residue is dissolved in 10 ml. of water. Onacidification with acetic acid 4-buty1amino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid solidifies and is filteredoff. The product is purified by recrystallization from acetic acid,yield 1.9 g. (82 percent), m.p. 225.

EXAMPLE 59 4-Butylamino-3-methyl-1H-pyrazolo[3 ,4b pyridine-5 carboxylicacid ethyl ester a. [[(3-methyl-5-isoxazolyl)amino]methylene]malonicacid diethyl ester 112.5 g. of 3-methy1-5-aminoisoxazole (1.14 mol. and248 g. of ethoxymethylene malonic acid diethyl ester (1.14 mol.) areheated with stirring for 45 minutes at 130. After this period, ethanolis removed under reduced pressure. The residue solidifies on cooling andis recrystallized from ethanol, m.p. 134-136, yield 245 g (80 percent).

b. 4-hydroxy-3-methylisoxazolo[3,4-b]pyridine-5- carboxylic acid ethylester 50 g. of [(3-methyl-5-isoxasolyl)amino]methylene]- malonic aciddiethyl ester (0.19 mol.) are quickly added to 250 ml. of vigorouslyrefluxing diphenyl ether. After 7 minutes, the reaction mixture iscooled rapidly. The solvent is distilled offin vacuo and the oilyresidue crystallizes after adding 100 ml. of methanol. Recrystallizationfrom methanol yields 20 g. (48 percent) of 4-hydroxy-3-methylisoxazolo[3 ,4-blpyridine-5- carboxylic acid ethyl ester, m.p. l50l52.

c. 4-ethoxy-3-methylisoxazolo[3,4-blpyridine-5- carboxylic acid ethylester 22.2 g. of 4-hydroxy-3-methylisoxazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (0.1 mol.) are dissolved in 150ml. of ethanol and 28 g. of potassium carbonate (0.2 mol.). 31 g. ofethyl iodide (0.2 mol.) are added. The mixture is heated with stirringfor 6 hours. The hot solution is filtered and the solvent evaporated.The oily residue yields on crystallization with methanol 18.2 g. of4-ethoxy-3-methylisoxazolo[3,4- b]pyridine-5-carboxylic acid ethylester. (73 percent), m.p. 62.

d. 4-butylamino-3-methylisoxazolo[3,4-blpyridine-5- carboxylic acidethyl ester Twenty-five g. of 4-ethoxy-3-methylisoxazolo[3,4-blpyridine-S-carboxylic acid ethyl ester (0.113 mol.) are dissolved in100 ml. of benzene and after adding 8 g. of butylamine (0.23 mol.), thesolution is refluxed for 12 hours. The solvent is distilled off and theresidual 4-butylamino-3-methylisoxazolo[3,4-b1pyridine-5- carboxylicacid ethyl ester is recrystallized from ligroin, m.p. 60, yield 23.5 g.(85 percent).

e. 3-acetyl-4-butylamino-2-hydroxypyridine5- carboxylic acid ethyl esterThree hundred g. of 4-butylamino-3-methylisoxazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester (1.08 mol.)are dissolved in 0.5 l. of acetic acid, 1 g. of palladium on charcoal isadded and the mixture is hydrogenated. After absorption of 24 1. ofhydrogen, the reaction is stopped, the catalyst is filtered off and thesolvent removed in vacuo. The remaining residue is treated for 7 hoursat 100 with 0.5 l. of water with stirring. The reaction mixture iscooled and extracted 3 times with 200 ml. portions of chloroform. Theorganic layers are collected, dried over sodium sulfate and evaporatedto dryness. Recrystallization of the oily residue yields 216 g. of3-acetyl-4- butylamino-2-hydroxypyridine-5-carboxylic acid ethyl ester(72 percent), m.p. 134136.

f. 4-butylamino-2-chloro-3-(a-chloro)vinylpyridine-S- carboxylic acidethyl ester 66.5 g. of 3-acetyl-4-butylamino-2-hydroxypyridine-5-carboxylic acid ethyl ester (0.24 mol.), 250 ml. of phosphrousoxychloride and 1 ml. of pyridine are heated for 3 hours at 40 withstirring. After this period the temperature is raised to 70 and kept for3 hours.

For 3 additional hours the mixture is agitated at 100. The excess ofphosphorous oxychloride is removed in vacuo and the residual oilcarefully neutralized with saturated sodium bicarbonate solution andthen extracted three times with 300 ml. portions of ether. The etherlayers are collected, dried over sodium sulfate and the solvent isdistilled. 750 ml. of ligroin are added to the remaining oil and thesuspension is agitated with 5 g. of charcoal under reflux for 30minutes. After flltration and evaporation of the ligroin, a pale yellowoil is obtained which yields on crystallization with a methanol/watermixture 46 g. of 4butylamino-2-chloro-3-(a-chloro)vinylpyridine-S-carboxylic acid ethyl ester (59 percent), m.p.4l42. g. 4-butylamino-3-methyl-lH-pyrazolo[3,4-b1pyridine- S-carboxylicacid ethyl ester To a mixture of 16 g. of hydrazine hydrate (0.32 mol.)in 200 ml. of alcohol, 31.6 g. of 4-butylamino-2-chloro-3-(a-chloro)-vinylpyridine-5-carboxylic acid ethyl ester (0.1mol.) in 50 ml. of alcohol are dropped in within 15 minutes withstirring at 30. The temperature is maintained for two additional hoursand then raised to After 8 hours, the solvent is distilled off and thecrystalline residue is treated with ml. of water. Filtration yields 22.6g. of 4-butylamino-3- methyl-l H-pyrazolo[ 3,4-b ]-pyridine 5carboxylicacid ethyl ester (82 percent), which is recrystallized from methanol,m.p. l72-174.

EXAMPLE 60 a. 4-Butylamin0-3-methyll H-pyrazolo[ 3,4-b]pyridine-5-carboxylic acid Five g. of4butylamino-3-methyl-1H-pyrazolol3,4- b]pyridine-5-carboxylic acid ethylester (0.019 mol.) are dissolved in 30 ml. of alcohol and treated with3.4 g. of potassium hydroxide (0.6 mol.) for 48 hours at 40. After thisperiod, the solvent is evaporated and the residue acidified with aceticacid. On addition of 30 ml. of water the4-butylamino-3-methyl-lH-pyrazolo[3,4- blpyridine-S-carboxylic acidcrystallizes. Filtration and recrystallization from dimethylformamideyields 3.6 g. (77 percent), m.p. 245-250.

EXAMPLE 61 4-Butylamino-3-methyl-l H-pyrazolo[3 ,4-b ]pyridine-5-carboxylic acid ethyl ester a. 3-acetyl-4-butylamino-2-chloropyridine-5-carboxylic acid ethyl ester Twenty-eight g. of 3-Acetyl-4-butylamino-2-hydroxypyridine-S-carboxylic acid ethyl ester (0.1 mol.) are dissolvedin 200 ml. of dry benzene and agitated with 50 ml. of phosphorusoxychloride for 24 hours at 60. After this time, the benzene and excessphosphorus halide are removed in vacuo, the residue carefully isneutralized with saturated sodium bicarbonate solution and extractedwith ether. The combined ether layers are dried over sodium sulfate, andevaporated to dryness. Recrystallization of the residue from ligroinyields 2.5 g. of 3-acetyl-4-butylamino-2- chloropyridine-S-carboxylicacid ethyl ester, m.p. b.4-buty1amino-3-methyl-lH-pyrazolo[3,4-b]pyridine- S-carboxylic acidethyl ester 1.4 g. of 3-acetyl-4-butylamino-Z-chloropyridine-5-carboxylic acid ethyl ester (0.005 mol.) are dissolved in 5 ml. ofalcohol and 0.5 g. of hydrazine hydrate (0.01 mol.) are added. Themixture is refluxed for 5 hours.

After this time, on addition of 10 ml. of water, 0.9 g. of4-butylamino-3-methyl-l H-pyrazolo[3 ,4- b]pyridine-carboxylic acidethyl ester crystallizes on cooling (69 percent), m.p. l72-l74.

EXAMPLE 62 4-lButylamino-1H-pyrazolo[3,4-b]pyridine-5- carboxylic acidethyl ester a. 4-butylamino-2-chloro-5-ethoxycarbonylpyridine-3-aldehyde The starting material 4-butylaminoisoxazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester is obtained by the sameprocedure described in Example 59 using 5- aminoisoxazole instead of3-methyl-5-aminoisoxazole.

26.3g. of 4-butylaminoisoxazolo[3,4-blpyridine-5- carboxylic acid ethylester (0.1 mol.) are dissolved in 100 ml. of alcohol, 1 g. of palladiumon charcoal is added and the mixture is hydrogenated. After absorptionof the theoretical amount of hydrogen, the reaction is stopped and thecatalyst is filtered off. The solvent is removed in vacuo. To theremaining oily residue 100 ml. of phosphorus oxychloride are added. Thereaction mixture is heated at 100 for 7 hours with stirring. The excessphosphorus oxychloride is distilled off and the residue is poured intoice water, followed by neutralization with saturated sodium bicarbonatesolution. The aqueous phase is extracted three times with 200 ml.portions of chloroform. The organic layers are I collected, dried ovesodium sulfate and evaporated to dryness. Recrystallization yields 8 g.of 4-butylamino-2- chloro-5-ethoxycarbonylpyridine-3-aldehyde, m.p.8688, yield 28 percent. b. 4-butylamino-1H-pyrazolo[3 ,4-b]pyridine-5-carboxylic acid ethyl ester 2.8 g. of 4-butylamino-2-chloro-5-ethoxycarbonylpyridine-3-aldehyde (0.01 mol.) are dissolved in 10 ml. ofalcohol and 1.5 g. of hydrazine hydrate (0.03 mol.) are added. Themixture is refluxed for 3 hours, cooled and diluted with 50 ml. ofwater. The crystalline precipitate of 4-butylamino-1H- pyrazolo[3,4-blpyridine-S-carboxylic acid ethyl ester is filtered andrecrystallized from diethyl ether, m.p. 18]", yield 2.2 g. (84.percent).

EXAMPLE 63 4-Butylamino-l ,3-dimethyl-1 H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester To a mixture of 4.6 g. ofmethylhydrazine (0.1 mol.) in 50 ml. of alcohol 10.5 g. of4-butylamino-2-chloro-3- (a-chloro)-vinylpyridine-S-carboxylic acidethyl ester (0.033 mol.), as obtained in Example 43, in 50 ml. ofalcohol are dropped in within minutes with stirring at 30. Thetemperature is maintained for two additional hours and then raised to80. After 8 hours, the solvent is distilled off, and the crystallineresidue is treated with 100 ml. of water. Filtration yields 7.2 g. of4-butylamino-1,3-dimethyl-lH-pyrazolo[3 ,4- b]pyridine-5-carboxylic acidethyl ester (75 percent) which is recrystallized from ligroin, m.p.5860.

The following additional compounds are produced by the procedure of theforegoing example by replacing the methylhydrazine with theappropriately R- substituted hydrazines:

4-n-Butylamino-1-ethyl-6-methyl-lH-pyrazolo[3,4- b]pyridine-5-carboxylicacid ethyl ester a. l-Ethyl-6-methyl-4-hydroxy-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester 51.1 g. ofl-ethyl-S-aminopyrazole (0.46 mol.) and 101 g. of acetomalonic acidethyl ester (0.5 mol.) are added to 224 g. of polyphosphorous acid. Themixture is heated with stirring at 120 for three hours. After thisperiod, the mixture is cooled, diluted with 1,000 ml. of water andsubsequently extracted twice with 300 ml. portions of chloroform. Thechloroform layers are collected, dried over sodium sulfate and thesolvent is distilled off. Recrystallization of the residue (67 g.) withpetroleum ether yields 1-ethyl-6-methyl-4-hydroxy-1H-pyrazolo-[3,4-b]pyridine-5-carboxylic acid ethyl ester, m.p. l18120. b.4-Chloro-1-ethyl-6-methyl-lH-pyrazolo[3 ,4- b]pyridine-5-carboxylic acidethyl ester A mixture of 49.1 g. of1-ethyl-6-methyl-4-hydroxyll-l-pyrazolo[3,4-bIpyridine-S-carboxylic acidethyl ester (0.197 mol.) and 250 ml. of phosphorous oxychloride isrefluxed for 4 hours. Then the excess phosphorous oxychloride is removedby vacuum distillation and the residue is treated with water. The4-chloro compound (42 g.) is filtered under suction and recrystallizedfrom n-hexane, m.p. 5456. c.4-n-Butylamino-1-ethyl-6-methyl-ll-l-pyrazol0[3 ,4-blpyridine-S-carboxylic acid ethyl ester To a solution of 10.7 g. of4-chloro-l-ethyl-6-methyl- 1H-pyrazolo[3,4-b]pyridine-S-carboxylic acidethyl ester (0.04 mol.) in 50 ml. of benzene are added 5.85 g. ofn-butylamine (0.08 mol.). The mixture is kept at room temperature for 4days. After this period, the precipitated butylamine hydrochloride isfiltered under suction and the filtrate is evaporated in vacuo todryness. The residue,4-n-butylaminol-ethyl-6-methyllH-pyrazolo[3,4-b]-pyridine-5-carboxylicacid ethyl ester, is recrystallized from n-hexane, m.p. -77, yield 9.0g.

EXAMPLE 68 4-n-Butylaminol -ethyl-3 ,6-dimethyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester hydrochloride Bysubstituting an equivalent amount of 1-ethyl-3- methylS-aminopyrazolefor the l-ethyl-S- aminopyrazole in the procedure of Example 670,l-ethyl-3,6-dimethyl-4-hydroxy-lH-pyrazolo[3,4- b]pyridine-5-carboxylicacid ethyl ester. m.p. 75-77, is obtained. This is then converted viathe 4-chloro compound to the 4-n-butylamino-l-ethyl-3,6-dimethyl-1H-pyrazolo-[3,4-b1pyridine-5-carboxylic acid ethyl ester (according tothe procedure of Examples 67b and 67c). The resulting oil dissolved inanhydrous ether forms with an alcoholic solution of hydrogen chloridethe hydrochloride salt, m.p. 153154 (ethyl acetate).

What is claimed is: l. A compound of the formula wherein R is hydrogenor alkyl up to 12 carbon atoms, R, is hydrogen, lower alkyl, phenyl,benzyl or phenethyl, benzoyl or halobenzoyl, R is hydrogen, phenyl orC,C alkyl, R,, and R each is hydrogen, lower alkyl, allyl, loweralkanoyl, R,,, R-,-phenyl, R,,, R phenyllower alkyl, di-loweralkylamino-lower alkyl, R,,, R benzoyl, methane sulfonyl,benzenesulfonyl, toluenesulfonyl or is -pyrrolidino, R is hydrogen,phenyl or C,C;, alkyl, R is hydrogen, halogen, lower alkyl,trifluoromethyl, amino or carboxy, R is hydrogen, halogen or loweralkyl, and physiologically acceptable acid addition salts thereof.

2. A compound as in claim 1 wherein R and R, each is lower alkyl, and RR,,, R, and R each is hydrogen. 3. A compound as in claim 1 wherein R,R, and R each is lower alkyl and R,, R, and R each is hydrogen. 4. Acompound as in claim 1 wherein R, R,, R and R each is lower alkyl, R, isC,C,, alkyl and R is hydrogen.

5. A compound as in claim 1 wherein R, R,, R and R,, each is lower alkyland R and R each is hydrogen.

6. A compound as in claim 2 wherein each lower alkyl group is ethyl.

7. A compound as in claim 3 wherein R and R, each is ethyl and R isbutyl.

8. A compound as in claim 4 wherein R, R,, R and R each is ethyl and Ris methyl.

9. A compound as in claim 5 wherein each lower alkyl group is ethyl.

10. A compound as in claim 3 wherein R is ethyl, R, is methyl and R isbutyl.

11. A compound as in claim 1 wherein R, and R each is lower alkyl andR,, R,, and R is hydrogen and R is C,-C alkyl.

12. A compound as in claim 11 wherein R is ethyl, R is methyl and R,, isbutyl.

13. A compound as in claim 1 wherein R, R,, and R each is lower alkyland R and R,, each is hydrogen and R is C,-C alkyl.

14. A compound as in claim 13 wherein R is ethyl, R, and R each ismethyl and R is butyl.

15. A compound as in claim 1 wherein R, R,, R,, and R each is loweralkyl and R and R,, each is hydrogen.

16. A compound as in claim 15 wherein R and R, each is ethyl, R is butyland R is methyl.

17. A compound as in claim 1 wherein R, R,, R R and R each is loweralkyl and R is hydrogen.

18. A compound as in claim 17 wherein R and R, each is ethyl, R and Reach is methyl and R is butyl.

19. A compound as in claim 1 wherein R, R,, R R and R each is hydrogenand R is lower alkanoyl.

20. A compound as in claim 1 wherein R is hydrogen.

21. A compound as in claim 1 wherein R is hydrogen or lower alkyl, R, ishydrogen, methyl, ethyl or butyl, R is hydrogen or methyl, R is ethyl,propyl or butyl, R is hydrogen or ethyl and R,, is hydrogen or methyl.

22. A compound as in claim 20 wherein R is nonyl, R, is ethyl, R and R,,each is hydrogen and R,, is butyl.

2. A compound as in claim 1 wherein R and R1 each is lower alkyl, andR2, R3, R4 and R5 each is hydrogen.
 3. A compound as in claim 1 whereinR, R1 and R3 each is lower alkyl and R2, R4 and R5 each is hydrogen. 4.A compound as in claim 1 wherein R, R1, R3 and R4 each is lower alkyl,R2 is C1-C3 alkyl and R5 is hydrogen.
 5. A compound as in claim 1wherein R, R1, R3 and R4 each is lower alkyl and R2 and R5 each ishydrogen.
 6. A compound as in claim 2 wherein each lower alkyl group isethyl.
 7. A compound as in claim 3 wherein R and R1 each is ethyl and R3is butyl.
 8. A compound as in claim 4 wherein R, R1, R3 and R4 each isethyl and R2 is methyl.
 9. A compound as in claim 5 wherein each loweralkyl group is ethyl.
 10. A compound as in claim 3 wherein R is ethyl,R1 is methyl and R3 is butyl.
 11. A compound as in claim 1 wherein R,and R3 each is lower alkyl and R1, R4 and R5 is hydrogen and R2 is C1-C3alkyl.
 12. A compound as in claim 11 wherein R is ethyl, R2 is methyland R3 is butyl.
 13. A compound as in claim 1 wherein R, R1, and R3 eachis lower alkyl and R4 and R5 each is hydrogen and R2 is C1-C3 alkyl. 14.A compound as in claim 13 wherein R is ethyl, R1 and R2 each is methyland R3 is butyl.
 15. A compound as in claim 1 wherein R, R1, R3 and R5each is lower alkyl and R2 and R4 each is hydrogen.
 16. A compound as inclaim 15 wherein R and R1 each is ethyl, R3 is butyl and R5 is methyl.17. A compound as in claim 1 wherein R, R1, R2, R3 and R5 each is loweralkyl and R4 is hydrogen.
 18. A compound as in claim 17 wherein R and R1each is ethyl, R2 and R5 each is methyl and R3 is butyl.
 19. A compoundas in claim 1 wherein R, R1, R2, R4 and R5 each is hydrogen and R3 islower alkanoyl.
 20. A compound as in claim 1 wherein R5 is hydrogen. 21.A compound as in claim 1 wherein R is hydrogen or lower alkyl, R1 ishydrogen, methyl, ethyl or butyl, R2 is hydrogen or methyl, R3 is ethyl,propyl or butyl, R4 is hydrogen or ethyl and R5 is hydrogen or methyl.22. A compound as in claim 20 wherein R is nonyl, R1 is ethyl, R2 and R4each is hydrogen and R3 is butyl.